LSD1 is a demethylation enzyme of histone, catalyzes a demethylation reaction of a monomethylated product and a dimethylated product of the 4th lysine residue of histone H3 (H3K4me1/2), and forms formaldehyde as a by-product. In addition, LSD1 forms a complex with flavin adenine dinucleotide (FAD) which is a kind of coenzyme, and FAD promotes oxidation of lysine residue by enzymes as a redox mediator.
WO 2010/084160 (patent document 1) discloses a compound of the following formula or a pharmaceutically acceptable salt thereof as an LSD1 inhibitor:

wherein R1-R5 are H, halo and the like; R6 is H or alkyl; R7 is H, alkyl or cycloalkyl; R8 is -L-heterocyclyl or -L-aryl wherein L is —(CH2)n—(CH2)n—, —(CH2)nNH(CH2)n—, —(CH2)nO(CH2)n— or —(CH2)nS(CH2)n—, and n is 0, 1, 2 or 3.
WO 2010/043721 (patent document 2) discloses a compound of the following formula or a pharmaceutically acceptable salt thereof as an LSD1 inhibitor:
wherein R1-R5 are H, halo and the like; R6 is H or alkyl; R7 is H, alkyl or cycloalkyl; R8 is —C(═O)NRxRy or —C(═O)Rz wherein Rx and Ry are each independently H, alkyl and the like, and Rz is H, alkoxy and the like.
WO 2011/035941 (patent document 3) discloses a compound of the following formula or a pharmaceutically acceptable salt thereof as an LSD1 inhibitor:(A′)x-(A)-(B)-(Z)-(L)-(D)  Iwherein (A′) is aryl, arylalkoxy, heterocyclyl and the like; (A) is heteroaryl or aryl; X is 0, 1, 2 or 3; (B) is a cyclopropyl ring; (Z) is —NH—; (L) is —CH2CH2— and the like; (D) is —N(—R1)-R2, —O—R3 or —S—R3 wherein R1 and R2 are each independently H, alkyl and the like; and R3 is H, alkyl and the like.
WO 2011/042217 (patent document 4) discloses a compound of the following formula or a pharmaceutically acceptable salt thereof as an LSD1 inhibitor:(A′)x-(A)-(B)-(Z)-(L)-C(═O)NH2  (I)wherein (A′) is aryl, arylalkoxy, arylalkyl, heterocyclyl and the like; (A) is heteroaryl or aryl; X is 0, 1, 2 or 3; (B) is a cyclopropyl ring; (Z) is —NH—; (L) is —(CH2)mCR1R2- wherein m is 0, 1, 2, 3, 4, 5 or 6; and R1 and R2 are each independently H or C1-6 alkyl.
US2010/0324147 (patent document 5) discloses a compound of the following formula or a salt thereof as an LSD1 inhibitor:
wherein X is a bond, O, S or NH; and RA, RB, RC, RD and RE are each independently H, C1-7 alkyl and the like.
WO 2010/143582 (patent document 6) discloses a compound of the following formula or a pharmaceutically acceptable salt thereof as an LSD1 inhibitor:
wherein R1 is H, an alkyl group optionally having a substituent attached thereto and the like; R2 is an alkylene group optionally having a substituent attached thereto; R3 is an alkyl group optionally having a substituent attached thereto, a phenyl group optionally having a substituent attached thereto and the like; R4 is an alkyl group optionally having a substituent attached thereto, a phenyl group optionally having a substituent attached thereto and the like; and X is O, NH2, NHCO, CONH, S or CH2.
J. Am. Chem. Soc. 2010, 132, 6827-6833 (non-patent document 1) discloses compounds of the following formulas as an LSD 1/2 inhibitor:

The Journal of Neuroscience, Oct. 17, 2007, 27(42): 11254-11262 (non-patent document 2) discloses that a decrease in histone H3K4 methylation and a decrease in Gad1 mRNA expression are observed in the brain of schizophrenia patients.